Estimation of the depth to the fresh-water/salt-water interface from vertical head gradients in wells in coastal and island aquifers |
| |
| Authors: | Scot K Izuka Stephen B Gingerich |
| |
| Institution: | (1) US Geological Survey, 677 Ala Moana Blvd., Suite 415, Honolulu, HI 96813 USA Fax: +1-808-522-8298 e-mail: skizuka@usgs.gov, US |
| |
| Abstract: | An accurate estimate of the depth to the theoretical interface between fresh, water and salt water is critical to estimates
of well yields in coastal and island aquifers. The Ghyben–Herzberg relation, which is commonly used to estimate interface
depth, can greatly underestimate or overestimate the fresh-water thickness, because it assumes no vertical head gradients
and no vertical flow. Estimation of the interface depth needs to consider the vertical head gradients and aquifer anisotropy
that may be present. This paper presents a method to calculate vertical head gradients using water-level measurements made
during drilling of a partially penetrating well; the gradient is then used to estimate interface depth. Application of the
method to a numerically simulated fresh-water/salt-water system shows that the method is most accurate when the gradient is
measured in a deeply penetrating well. Even using a shallow well, the method more accurately estimates the interface position
than does the Ghyben–Herzberg relation where substantial vertical head gradients exist. Application of the method to field
data shows that drilling, collection methods of water-level data, and aquifer inhomogeneities can cause difficulties, but
the effects of these difficulties can be minimized.
Received, April 1997 · Revised, January 1998 · Accepted, January 1998 |
| |
| Keywords: | USA numerical modeling salt-water/fresh-water relations coastal aquifers vertical head gradients |
| 本文献已被 SpringerLink 等数据库收录！ |
|
